1. Field of the Invention
Embodiments of the present invention generally relate to a suspension system, more particularly, a shock absorber with multiple reservoir chambers (IFPs), especially one permitting selective communication between the reservoirs and a main damper chamber.
2. Description of the Related Art
Integrated damper/spring vehicle shock absorbers often include a damper body surrounded by a mechanical spring. The damper consists of a piston and shaft telescopically mounted in a fluid filled cylinder. The purpose of the damper is to control the speed at which the shock absorber operates. The mechanical spring provides resistance to shock events and may be a helically wound spring that surrounds the damper body. Various integrated shock absorber configurations are described in U.S. Pat. Nos. 5,044,614, 5,803,443, 5,553,836 and 7,293,764; each of which is herein incorporated in its entirety by reference. A shock absorber of U.S. Pat. No. 7,293,764 is shown herein as FIG. 1. As shown, the shock absorber 10 comprises a damper assembly 15 consisting of a chamber 18 housing a piston (not shown) and rod 20 and a helical spring 25 disposed on the damper in a manner whereby the spring and damper operate together. The shock absorber is attached via eyeholes 30, 35 to separate portions of a vehicle (not shown) and the shock operates when there is relative movement between those portions.
Various arrangements permit aspects of the shock absorber to be adjusted or changed by an end user. For example, U.S. Pat. No. 5,044,614 (“614 patent”) shows a damper body carrying a thread 42. A helical spring 18 surrounds the damper body. The compression in the helical spring 18 may be pre-set by means of a nut 48 and a lock nut 50. The nut 48 may be translated axially relative to the body (“tube”) 16 and thread 42 by rotating the nut 48 around the threaded sleeve 42. Rotation of the nut 48 in a given direction (e.g. clockwise as viewed from end 44 for a right hand thread 42) will cause the nut to move toward the retainer clip 26 thereby compressing spring 18 between the nut 48 and the retainer clip 26. Once the spring 18 is in a desired state of compression, lock nut 50 is rotated, using a wrench, up against nut 48 and tightened in a binding relation therewith.
Some shock absorbers utilize gas as a spring medium in place of, or in addition to, mechanical springs. Gas spring type shock absorbers, having integral dampers, are described in U.S. Pat. Nos. 6,135,434, 6,360,857 and 6,311,962, each of which is herein incorporated in its entirety by reference. U.S. Pat. No. 6,360,857 shows a shock absorber having selectively adjustable damping characteristics. U.S. Pat. No. 7,163,222, which is incorporated herein in its entirety by reference, describes a gas sprung front shock absorber for a bicycle (a “fork”) having a selective “lock out” and adjustable “blow off” function.
The spring mechanism (gas or mechanical) of some shock absorbers is adjustable so that it can be preset to varying initial states of compression. In some instances, the shock spring (gas or mechanical) may comprise different stages having varying spring rates thereby giving the overall shock absorber a compound spring rate depending varying through the stroke length. In that way the shock absorber can be adjusted to accommodate heavier or lighter carried weight, or greater or lesser anticipated impact loads. In vehicle applications, including motorcycle and bicycle applications and particularly off-road applications, shock absorbers are pre-adjusted to account for varying terrain and anticipated speeds and jumps. Shocks are also adjusted according to certain rider preferences (e.g. soft-firm).
A type of integrated spring/damper shock absorber, having a gas spring, is shown in FIG. 28, for example, of U.S. Pat. No. 7,374,028, which is incorporated herein in its entirety by reference. The shock shown in FIG. 28 of the '028 patent also includes an “adjustable intensifier assembly 510.” That intensifier or “reservoir” accepts damping fluid from chamber 170 as the fluid is displaced from that chamber by the incursion of rod 620 into chamber 170 during a compression stroke of the shock. The intensifier valve assembly regulates flow of damping fluid into and out of the reservoir, and an embodiment of the valve assembly is shown in FIG. 17 of the patent.
In some instances, reservoir portions of dampers are separate components whereby a separate chamber is provided for fluid expelled from the main chamber. A damper with such a remote reservoir is illustrated in FIG. 9 of the '028 patent incorporated herein. Other suspension systems use multiple, separate reservoir-type chambers that divide the usable dampening capability of the shock. In these designs, fluid is pushed from the main dampening cylinder and with valving, the reservoir chambers are utilized in various ways. By using one or both chambers, the travel available in the shock can be determined by a user. Configurations of multiple reservoir-type shocks are shown in U.S. Pat. No. 7,219,881, which is incorporated herein in its entirety by reference. The presently available dual reservoir designs have drawbacks. For example, utilization of both reservoirs is achieved solely by use of two separate and distinct paths between the main chamber and each of the reservoirs. Because each path has its own metering devices, especially in the rebound direction, there is always a potential of one of the reservoir chambers to lose fluid and “crash” when the metering devices are set differently.
What is needed is a multiple reservoir suspension system that ensures that each reservoir retains sufficient operating fluid. What is needed is a multiple reservoir system having simplified controls.